initial work, and every one else who has tested things for me.
this is largely my fault at this point :-)
the main changes are something like:
- usbd_bus_methods{} gains a get_lock() to enable the
host controller to provide a lock for the USB code.
if the lock isn't provided, old-style protection is
(partially) applied.
- ehci/ohci/uhci have been converted to the new
interfaces, including mutex/cv/etc conversion.
- usbdivar.h contains a discussion about locking and
what locks are held for which method calls. more
to come for usbdi(9) here.
- audio drivers (uaudio, umidi, auvitek) have been
properly SMPified now that USB is ready.
- scsi drivers have been modified to take the kernel
lock explicitly before calling into scsi code.
- usb pipes are associated with a lock, that is the
same as the controller lock. (this could be split
up further in the future.)
- several usbfoo_locked() or usbfoo_unlocked()
functions have been added to the usbdi(9) to
enable functionality with or without the USB
lock (per controller) already being held.
the TODO.usbmp file has specific details on what is left to
do, including what device-specific changes should be done now
that the whole framework is ready.
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